Lock joint for sheet metal



y 1940- A. G. SIEBENLIST 2,201,409

LOCK JOINT FOR SHEET METAL 2 Sheets-Sheet 1 Filed May 4, 1938 INVENTOR TTORNEY W y 3949- A. G. SIEBENLIST 2,201,409

LOCK JOINT FOR SHEET METAL 2 Sheets-She et 2 Filed May 4, 1938 Fig.8. F 7 l VENTOR l war 6 W manna May 21, 1940 2,201,409

UNITED STATES PATENT OFFICE 2,201,409 LOCK JOINT FOR SHEET METAL Anthony G. Siebenlist, Milwaukee, Wis., assignor to Milcor Steel Company, Milwaukee, Wis., a corporation of Delaware Application May 4, 1938, Serial No. 205,998 3 Claims. (Q1. 138-74) This invention relates to joints or seams for Figure 2is an enlarged fragmentary perspective joining the edges of thin metal sheets, and more view of the left end portion of the pipe shown particularly for sheet metal pipe, such as stovein Fig. l. pipe or the like. Figures 3, 4 and are enlarged transverse sec- Among the objects of the invention are to tions, respectively taken along the lines 3-3, 5 provide a joint which may be easily and quickly and of ut w th the longitudieffected without the use of special tools and which nal joint closed. when assembled is permanent and substantially Figure 6 is a fragmentary longitudinal section leak-proof and rigidly resistant to any material of the closed joint taken along line 6-6 of Fig. 3. in relative displacement of the joined sheets. It is Figure '7 is a diagram indicating the relative 10 a particular object of the invention to provide an overlapping of seams of longitudinally telescoped improved longitudinal joint or seam for stovepipe sections of the ty herein w pipe, which will permit joining of the edges at the Figure 8 is a diagram indicating the manner in place of sale or use and which when joined will which sheet metal pipe sections of the type herei provide a substantially leak-proof structure rigidin shown may be nested for shipment. 5

ly prevented from opening up at the joint and The pipe section shown in Fig. 1 is made of an likewise prevented from any longitudinal shifting appropriate thickness of metal sheet formed to of the joined edges relative to one another, such approximate a circle of the desired pipe diameter. for example as might otherwise occur in the The adjacent longitudinal edges of the metal forcing of the end of one section of pipe inside Sheet are formed to be interlockingb' fi e t 20 another adjacent section. v gether, the one edge, generally identified by the Afurther purpose, particularly relating to sheet numeral 2 being adapted to enter between suitmetal pipe, such as stovepipe and the like, is to able folds in the other edge generally identified effect an improved longitudinal joint in such by the numeral 3.

manner that one end of each pipe section is 'The folded edge 3 includes a folded portion 4, adapted to be fitted within a similar pipe sec- Fig. 2, inwardly and rearwardly extended, a retion, and the other end of the same section is turn folded portion 5 and another folded portion adapted to receive a similar pipe section, while 6. The folding provides a groove or slot 1 adapted maintaining the resulting pipe section substanto receive the portion 8 of the edge 2 throughout tially leak-proof atthe joint formed between the the length of the joint, and to resiliently and fric- 30 telescoped portions in spite of the thickness of tionally engage therewith. the longitudinal seam. At spaced intervals along the edge 2 there are Another object is to improve upon the locked formed lug or hook portions 9, 9, etc., these bejoint of my previous Patent No. 2,038,389, issued ing formed by displacing the sheet metal inward- April 21, 1936, particularly in preventing rela- 1y sufficiently that they may engage with and 5 tive longitudinal movement of the joined edges, hook over the inner edge of the folded portion 6, and particularly in providing an end structure as shown in Fig. 4, when the portion 8 is asfor telescoping the end portions of adjacent pipe sembled between the portions 4 and 6. The ensections while maintaining a ti ht joint at the easement of these hook or lug portions 9 with telescoped portion. the portion 6 looks the two edges against subse- 40 Another object is generally to simplify and imquent disengagement.

prove the construction and operation of joints At the left hand end, Fig. 1, there are t u k between metal sheets and still other objects will outhfrom the portion 8 a plurality of lug or ear be apparent from this specification. portions III, II. In the folded portion 4 metal is The invention resides in the structure herein cut away to form a slot or socket l2, Figs. 2 and 3. 45

illustrated, described and claimed, together-with When the portion 8 has been shoved forward, as

such modifications of the structure illustrated previously described, to interlock the joint the and described as may be equivalent to the struclugs Ill and H are received between the end faces ture of the claims. Ma and l2b of the slot II, the lugs springing out- Throughout the specification the same refwardly into the slot and fitting sufficiently closely 50 erence characters have been used for the same to prevent subsequent relative longitudinal moveparts, and in the drawings: ment of the interlocked edges.

Figure l is a view of a section of Stovepipe in- Pipe sections of the type herein shown are incorporating the invention, the longitudinal joint tended toeifect any desired length of conduit by a being shown open, telescoping one end of the section, such as the right hand end of Fig. 1, inside the adjacent left hand end of a similar section, crimped, as at A, telescoping, and provided with an enlargement, as at B, Fig. 1 to limit the amount of telescoping.

terlocking of lugs 9 on shown in Fig. 4 cannot always be relied upon to prevent outward distortion of the sheet metal of the edge 3, particularly since the resistance to this particular type the combined resiliency of the folded portions 4, 5 and G. In order to apply resistance to such distortion at a point which substantially avoids the resiliency of the folded portions the lugs Ill, II are formed with the corners Illa, Ha projecting to engage outside the folded portion 4, in the manner shown for the corner H a in Fig. 3.

It will be apparent that both the lug or hook portions 9, 9 and the lug or ear portions l0, ll operate to prevent lateral disengagement of the assembled edges to the right or left in Figs. 3, 4. Both types also prevent relative displacement of the edges upwardlyor downwardly in Figs. 3,4, but the structure of Fig. 3 is preferable in some respects, particularly at the end of the pipe section which telescopes outside adjacent similar sections for reasons just explained. Only the lugs of the type ill, I I operate to prevent relative longitudinal displacement of the edges, this effect resulting in part from the form of the lugs and in part from their longitudinal fit within the slot l2. It will be apparent that, if desired, the entire length of the joined edges maybe locked by the use of suitably spaced lugs such as I0, I l, providing that the edge 3 provides correspondingly spaced recesses or slots, such as l2.

Where sheet metal pipe sections are formed with a relatively thick longitudinal seam or joint, and the desired length of conduit is obtained by telescoping the one end of apipe section inside the end of an adjacent section, the thickness of the folded and engaged metal portions which form the seam is, unless prevented, the cause of objectionable leaks at the telescoped joint between sections. In a stovepipe for example such leaks may permit smoke or gas to escape or, if the conduit is of any considerable length,'may materially reduce the eifective chimney draft. The improved longitudinal joint herein disclosed avoids such leaks in the following manner:

At the end of the pipe section which is intended to telescope or engage inside of an adjacent section the portion'8 of the edge 2 is formed inwardly relative to the metal sheet, sufficiently that the outer surfaces 2a and 3aof the joint may substantially coincide with a circle of the same diameter as the exterior of the outside pipe at this point in spite of the thickness of the seam, which otherwise would prevent the pipe exterior from assuming a circular exterior form.

At the other end of the pipe section, that is say at the end which telescopes or engages outside the end of an adjacent pipe section, the portion 8 is formed outwardly and the edge 3 is oifset outwardly, asshown in Fig. 3, suificiently that the inner surface of the seam may substantially coincide with a circle of the same diameter as the interior of the pipe at this point in spite of the thickness of the seam, which would. otherwise prevent the pipe interior from assuming circular form.

The construction just referred to may be readof distortion is reduced by by comparison ofFigs. 3 and 4b! of nested shipment, as mentioned.

line seam is more convenient for lateral assemblyof the edge into the seam slot at point ,It results, of course, that the seams of not objectionable, since it is too slight to be ap parent in the resulting pipe lineand the thin sheet metal employed for stove p'pe is sufficiently resilient for the pipe line exterior to assume a form presenting a substantially cylindrical appearance throughout.

It will be understood that the novel results effected positely directed abutment edges,-said other longitudinally extended edge providing portions struck up from the plane of the metal to provide longitudinally spaced edges free of the sheet whereby to collectively prevent relative longitudinal movement of said engaged edges.

2. In a sheet metal pipe section the combination of a longitudinaljoint longitudinally extended edge engaging in said slot, said other longitudinally extended edge providing portions struck up from the plane of the metal to form longitudinally spaced abutment edges free of the sheet stock, and an interior side wall of said slot adjacent the exterior pipe sheet being apertured to provide oppositely directed longitudinally spaced abutment edges respectively v engaging with different of the first mentioned abutment edges during engagement of said other longitudinally extended edge with said slot to prevent relative longitudinal movement of the engaged longitudinally extended edges.

3. A sheet metal stove pipe section of generally cylindrical form in which one longitudinal edge of the pipe sheet is folded to provide a slot opening in the direction of the other edge and engaged thereby to form a longitudinal seam having a radial thickness materially greater than the thickness of the pipe sheet, said seam being of substantially straight line longitudinal extension throughout the length of the section, said pipe sheet being relatively offset to stand substantially flush with the exterior of said straight line seam in the sheet portions adjacent thereto at the one end of the pipe section, and relatively offset to stand substantially flush with the interior of said straight line seem in the sheet portions adjacent thereto at the other end of the pipe section.

ANTHONY G. SIEBENIJST. 

